Re: [git pull] drm for v4.15

From: Christian KÃnig
Date: Fri Nov 17 2017 - 13:14:48 EST

First of all I can certainly agree with everything said so far, so just skipping to the technical problem.

Am 17.11.2017 um 17:57 schrieb Linus Torvalds:

People say "it's a ton of work to do it by hand". They'd be right. I'm
not saying you should do it by hand. But "automation" does not always
need to mean "completely mindlessly stupid" either.

Taking an example from the AMD headers why this automation is more tricky than it sounds in the first place: Look at the mmVM_CONTEXT*_PAGE_TABLE_BASE_ADDR registers for example.

Register 0-7 are consecutive and so could be perfectly addressable with an index, but register 8-15 aren't and so we always end with logic like if(i<8) ... else ....

The rational from the hardware guys is obvious that they initially had only 8 and on a later hardware generation extended that to 16 registers.

Patterns like that repeat all over the place and are not limited to AMD at all.

We could write up hand written rules to sanitize all of that, but then we are back to "automatically" creating the headers by hand.

When you have to maintain 10+ years of hardware generations where sometimes registers headers even need to be regenerated from the database then that is something which won't fly either.

Certainly not saying that this is a bad idea, but we simply need better tools for that which also have 100% reproducible results.

Ideas welcome,